Red mud-based organic layered double hydroxide and method of preparation

Abstract

The application discloses a kind of red mud-based organic layered double hydroxide and preparation method, belong to organic layered double hydroxide technical field.A kind of red mud-based organic layered double hydroxide preparation method is as follows: with red mud as divalent metal ion and trivalent aluminum ion source, organic intercalation agent is used as organic anion source;Red mud, aluminum salt and organic intercalation agent are ball milled, and red mud and aluminum salt occur solid-phase coprecipitation and form positively charged iron-aluminum layered double metal hydroxide, and organic anion is inserted into the interlayer of iron-aluminum layered double metal hydroxide, to obtain red mud-based organic layered double hydroxide.The application uses red mud as raw material, and red mud-based organic layered double hydroxide is prepared by using ball milling method, which not only reduces cost and energy consumption, but also improves the utilization rate of red mud.

Description

Technical Field

[0001] This invention relates to the field of organic layered double hydroxides, and more specifically to a red mud-based organic layered double hydroxide and its preparation method. Background Technology

[0002] Organic layered double hydroxides (LDHs) refer to materials in which the interlayer domains contain organic anions or are functionalized through organic modification. Currently, the mainstream preparation methods for organic layered double hydroxides (LDHs) are hydrothermal methods or co-precipitation methods, both of which use high-purity chemical raw materials as the source of metal ions for the layers and organic intercalating agents.

[0003] Currently, the preparation of organic LDHs typically uses high-purity divalent metal salts (such as magnesium nitrate, magnesium chloride, zinc nitrate, etc.) and trivalent metal salts (such as aluminum nitrate, aluminum sulfate, etc.) as the source of metal ions for the LDH layers, ensuring the regularity and purity of the layer structure. Organic anions such as sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate are used as intercalating agents. Through ion exchange or co-precipitation, organic anions are inserted into the LDH layers to prepare organic LDH products. The preparation process employs either a hydrothermal method or a co-precipitation method. In the co-precipitation method, under specific temperature (25℃~60℃) and pH (9~11) conditions, a mixed solution of divalent and trivalent metal salts is slowly mixed with an alkaline solution (such as sodium hydroxide or ammonia), while simultaneously adding organic intercalating agents such as SDS. After stirring until sufficient precipitation, the mixture undergoes static crystallization, filtration, washing, and drying to obtain organic LDHs. This method is simple and the conditions are easy to control, but it requires strict control of the pH value and metal ion ratio of the reaction system, and the washing step is indispensable. The hydrothermal method involves mixing divalent metal salts, trivalent metal salts, organic intercalating agents (SDS), and alkaline solutions in a specific ratio, placing them in a high-pressure reactor, and reacting at 100-180℃ under high pressure for 4-24 hours. After the reaction, the mixture is cooled, filtered, washed, and dried to obtain organic LDHs. The product prepared by this method has a complete crystal form and a regular layered structure, but the reaction conditions are harsh and require a large amount of energy.

[0004] In summary, the existing technologies for preparing organic layered double hydroxides suffer from problems such as high raw material costs, low raw material utilization, large amounts of waste liquid generated during the preparation process, and high energy consumption. Summary of the Invention

[0005] To address the above problems, this invention provides a red mud-based organic layered double hydroxide and its preparation method. This invention uses red mud as raw material and employs a ball milling method for preparation, which not only reduces costs and energy consumption but also improves the utilization rate of red mud.

[0006] The first objective of this invention is to provide a method for preparing a red mud-based organic layered double hydroxide, which is prepared according to the following steps: Red mud was used as a source of divalent metal ions and trivalent aluminum ions, and an organic intercalating agent was used as a source of organic anions. The red mud, aluminum salt and organic intercalating agent were ball-milled, and the red mud and aluminum salt underwent solid-phase co-precipitation to form a positively charged iron-aluminum layered bimetallic hydroxide. The organic anions were intercalated into the interlayer of the iron-aluminum layered bimetallic hydroxide to obtain a red mud-based organic layered bimetallic hydroxide. The mass ratio of red mud to aluminum salt was 1:2 to 3.

[0007] Specifically, the core mechanism of the ball milling method for preparing organic LDHs is a mechanochemical-driven in-situ synthesis-intercalation coupling process: High-energy ball milling first refines and activates red mud, aluminum salts, and organic intercalating agents. Divalent metal ions in the red mud and trivalent aluminum ions from the aluminum salts and red mud undergo solid-phase co-precipitation under mechanically induced local hydrolysis and trace amounts of water vapor, forming positively charged hydrotalcite-like layers. Simultaneously, continuous impact and shear forces force organic anions into the newly formed interlayer spaces, replacing the original inorganic anions and expanding the layers, completing layer construction and organic intercalation in one step, ultimately obtaining organic LDHs with expanded interlayer spacing. The entire process requires no large amounts of solvent, is completed rapidly at room temperature, and can directly utilize red mud with complex components.

[0008] This invention uses the molar ratio of iron in red mud to aluminum in aluminum chloride to control the phase purity and layer composition of LDH. When the ratio is appropriate, a pure phase Fe / Al-LDH with good crystallinity and regular interlayer spacing can be formed. Excess aluminum can easily generate impurities such as aluminum hydroxide, while excess iron will leave unreacted iron oxides. Both of these will reduce the crystallinity and structural order of LDH, and at the same time affect the specific surface area and anion exchange capacity.

[0009] In a preferred embodiment of the present invention, the anion exchange capacity of the iron-aluminum layered bimetallic hydroxide formed by red mud and aluminum salt is used as a benchmark, and the added mass of the organic intercalating agent is 1.0 to 2.0 times the anion exchange capacity of the iron-aluminum layered bimetallic hydroxide.

[0010] In this invention, the iron-aluminum layered bimetallic hydroxide formed from red mud and aluminum salts is referred to as iron-aluminum LDHs.

[0011] Anion exchange capacity is based on Cl - The test was based on anion exchange. During the test, the anion exchange capacity of LDH was determined by ion chromatography: After vacuum drying of the LDH sample to constant weight, a certain mass was accurately weighed, and an excess of NaCl solution of known concentration was added. The mixture was then subjected to constant temperature shaking for 24 hours under CO2-free conditions to complete the interlayer anion exchange. After high-speed centrifugation, the supernatant was collected, and the remaining Cl₂ in the supernatant was determined using ion chromatography. - Concentration, and a blank control were performed simultaneously. Cl was calculated.- The consumption of [amount] is divided by the sample mass to obtain the anion exchange capacity (AEC) in mmol / g. Degassed water and nitrogen protection are required throughout the process to avoid carbonate interference and ensure Cl [concentration]. - Sufficient amount added, and thorough solid-liquid separation and washing.

[0012] In a preferred embodiment of the present invention, the ball milling speed is 350 rpm to 400 rpm. The speed determines the ball milling kinetic energy and activation intensity. If the speed is too low, the impact force is insufficient, the red mud is difficult to activate, ion diffusion is slow, LDH nucleation and crystallization are insufficient, and the product has low crystallinity and obvious impurities. When the speed is moderate, it can take into account both crushing activation and uniform nucleation, which can fully activate the red mud and form an orderly layered structure, resulting in LDH with high crystallinity and obvious layered characteristics. If the speed is too high, strong shear and local overheating will occur, leading to LDH layer fracture, structural amorphization, and even the appearance of oxide impurities, reducing structural integrity.

[0013] In a preferred embodiment of the present invention, during ball milling, dry milling is performed for 4 to 5 hours, followed by wet milling with water for 4 to 5 hours. Dry milling is mainly responsible for refining the raw materials, ensuring uniform mixing, and activating them mechanically and chemically. If the time is too short, the red mud will not be sufficiently activated, resulting in uneven mixing, low precursor activity, and difficulty in forming a complete LDH structure during subsequent wet milling. A moderate time can obtain a highly active amorphous precursor, providing a good foundation for wet milling crystallization, resulting in high crystallinity and pure phase of the LDH product. If the time is too long, it will cause cold welding and agglomeration of particles, overheating of the system, and disorder of the precursor, which will inhibit LDH crystallization and reduce the regularity of the layered structure.

[0014] In a preferred embodiment of the present invention, the ratio of red mud to water is 1g to 2g: 1ml. The amount of water added determines the slurry fluidity and ion mass transfer rate. When the amount of water is too small, the slurry becomes viscous, the grinding efficiency decreases, ion diffusion is hindered, LDH crystallization is incomplete, particle agglomeration is severe, and the pore structure is underdeveloped. When the amount of water is moderate, the fluidity is suitable, ion dissolution and diffusion are sufficient, which can promote the uniform nucleation and growth of LDH, forming a product with regular interlayer spacing, large specific surface area, and rich mesoporous structure. When the amount of water is too large, it will buffer the impact energy, weaken the mechanochemical effect, delay the crystallization process, and lead to a decrease in LDH crystallinity, larger grains, and poorer interlayer structure stability.

[0015] In a preferred embodiment of the present invention, the ball-to-material ratio during ball milling is 40–20:1. The ball-to-material ratio affects the grinding impact force and energy transfer efficiency. If the ratio is too low, it will lead to insufficient crushing of red mud, uneven mixing of raw materials, insufficient mechanochemical activation, and a high number of impurities in the product with poor LDH crystallinity. A moderate ratio can achieve efficient crushing, uniform mixing, and sufficient activation, which is conducive to the formation of LDH with a complete structure and regular flaky morphology. If the ratio is too high, it is easy to cause excessive particle refinement, lattice distortion, and severe agglomeration, which will destroy the layered structure of LDH and increase structural defects.

[0016] In this invention, the organic intercalating agent can be sodium dodecyl sulfate, sodium stearate, or fatty acid, and the aluminum salt can be aluminum chloride, aluminum oxide, or aluminum hydroxide. However, when the organic intercalating agent is sodium dodecyl sulfate and the aluminum salt is aluminum chloride, the preparation process is simpler and the product purity is higher.

[0017] In a preferred embodiment of the present invention, the organic intercalating agent is sodium dodecyl sulfate and the aluminum salt is aluminum chloride.

[0018] A second objective of this invention is to provide a red mud-based organic layered double hydroxide prepared by the above-described preparation method.

[0019] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses four core technical shortcomings of existing hydrothermal / coprecipitation methods for preparing organic layered double hydroxides: high raw material costs, heavy wastewater pollution, low resource utilization, and poor energy and safety. It utilizes a mechanochemical ball milling process, where ball milling causes divalent metal ions in red mud to undergo solid-phase coprecipitation with aluminum salts and trivalent aluminum ions from the red mud, forming positively charged hydrotalcite-like layers. Then, organic anions from an organic intercalating agent are embedded into the interlayer of these positively charged hydrotalcite-like layers, forming red mud-based organic layered double hydroxides. This method not only achieves the resource utilization of red mud but also realizes low-cost, green, high-utilization, and low-energy-consumption green preparation of organic layered double hydroxides, filling a gap in existing technologies and demonstrating significant technological advancement and application value. Specific advantages are as follows:

[0020] 1. Solve the technical problems of high raw material costs and limited industrial application of existing technologies.

[0021] Existing technologies employ hydrothermal / coprecipitation methods, relying entirely on high-purity chemical reagents (such as aluminum nitrate and magnesium chloride) as the metal ion source for LDHs layers. The production processes for these chemical raw materials are complex and purification costs are high, requiring strict pretreatment to ensure purity, directly increasing the preparation cost of organic LDHs. Furthermore, some technologies use nitrates as raw materials, which are not only costly but also pose potential explosion risks, requiring additional safety protection costs and severely restricting the large-scale industrial application of the product. This invention utilizes a mechanochemical ball milling process, using red mud (an industrial solid waste from bauxite alumina refining) as the main raw material, eliminating the need for high-purity chemical reagents to provide layer metal ions. Red mud is rich in divalent / trivalent metal ions such as magnesium, aluminum, and iron, which can be directly used as the core component of LDHs layers; only a small amount of aluminum chloride is needed to adjust the metal ion ratio to complete the preparation. This solution significantly reduces raw material costs while utilizing industrial solid waste resources, fundamentally solving the technical bottlenecks of high raw material costs and difficulty in large-scale production in existing technologies.

[0022] 2. Solve the technical problems of generating large amounts of waste liquid and causing serious environmental pollution in the existing preparation process.

[0023] Existing technologies utilize liquid-phase reaction systems (hydrothermal / coprecipitation methods), which present two key environmental challenges: firstly, the reaction process requires the addition of excess alkali to adjust the pH; secondly, multiple washings are necessary after the reaction to remove residual salt ions, both generating large amounts of saline wastewater. Direct discharge of this wastewater leads to water pollution and soil salinization; centralized treatment requires expensive wastewater treatment equipment and costs, contradicting the principles of green production. This invention employs a mechanochemical solid-phase ball milling process. The reaction system is solid-state, eliminating the need for a hydrothermal liquid-phase environment and the use of excess alkali to adjust the pH. The entire preparation process directly triggers the solid-phase chemical reaction through the mechanical forces (shearing, extrusion, friction) generated by ball milling, eliminating the possibility of wastewater generation at the source. This completely solves the environmental pollution problems of existing technologies, complies with environmental regulations, and eliminates the need for wastewater treatment costs.

[0024] 3. Solve the technical problems of low raw material utilization and serious resource waste in existing technologies.

[0025] Existing technologies, based on pure chemical raw materials, often fail to convert some metal ions into the target product during liquid-phase reactions due to incomplete reactions and washing losses, resulting in low raw material utilization. Simultaneously, red mud, a massive industrial solid waste, contains abundant metal ion resources that are not utilized by existing technologies, leading to both resource waste and solid waste accumulation. This invention uses red mud as the main raw material and employs the strong mechanical action of mechanochemical ball milling to fully disrupt the crystal structure of the red mud, releasing the metal ions to participate in the solid-phase reaction, significantly improving raw material utilization. Furthermore, it converts red mud into high-value-added organic LDHs materials, achieving the reduction and resource-based disposal of industrial solid waste, overcoming the resource waste shortcomings of existing technologies, and aligning with the sustainable development requirements under the dual-carbon development goals.

[0026] 4. Solve the technical problems of high energy consumption and significant safety hazards in existing technologies.

[0027] In existing technologies, the hydrothermal method requires reaction time of several hours to tens of hours under high temperature and high pressure conditions of 100-180℃, while the co-precipitation method requires long-term stirring, static crystallization, and subsequent high-temperature drying, resulting in high overall energy consumption. Furthermore, the high-temperature and high-pressure reaction environment poses safety hazards such as equipment damage and material leakage, and places stringent requirements on the corrosion resistance and sealing of production equipment, increasing production and operating costs. This invention employs a mechanochemical ball milling process, where the reaction is carried out at room temperature and pressure, eliminating the need for high-temperature and high-pressure conditions. The reaction is driven solely by the electrical energy of the ball mill, resulting in significantly lower energy consumption than the hydrothermal and co-precipitation methods. Simultaneously, the solid-phase reaction system avoids the safety risks associated with high temperature and high pressure, simplifies production equipment requirements, further reduces production costs, and enhances the safety and stability of the technology. Attached Figure Description

[0028] Figure 1 This is a flowchart of the preparation of organic LDHs in Example 1 of the present invention.

[0029] Figure 2 The infrared spectrum of the organic LDHs prepared in Example 1 is shown.

[0030] Figure 3 The images show the XRD patterns of the organic LDHs and red mud prepared in Example 1.

[0031] Figure 4 for Figure 3 A magnified view of a portion of the image. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] The red mud used in this invention consists of the following components by mass percentage: silicon dioxide, 16.16%; aluminum chloride, 22.52%; iron oxide, 33.41%; calcium oxide, 3.32%; sodium oxide, 8.64%; and titanium dioxide, 5.5%.

[0034] Example 1 This embodiment provides a method for preparing a red mud-based organic layered double hydroxide, the preparation flow chart of which is shown below. Figure 1 As shown, the specific operation steps are as follows: Step 1: Add the red mud to a beaker, wash it with 100 ml of deionized water and ethanol respectively, centrifuge, dry at 100℃, and set aside.

[0035] Step 2: Add 4g of red mud and 8g of aluminum chloride at a mass ratio of 2:1. Weigh out 25.95g of sodium dodecyl sulfate (SDS) to be added at a rate 1.5 times the anion exchange capacity of the iron-aluminum LDHs. Mix the red mud, aluminum chloride, and SDS together and place them in a ball mill. Set the speed to 350 rpm and the ball-to-material ratio to 30:1. During ball milling, first dry mill for 4 hours, then add water for wet milling for 4 hours, adding 4 mL of water. Organic LDHs are obtained. The grinding media used during grinding is zirconium balls. The ball-to-material ratio refers to the ratio of the mass of the zirconium balls to the total mass of the red mud, aluminum chloride, and sodium dodecyl sulfate.

[0036] Example 2 This embodiment provides a method for preparing a red mud-based organic layered double hydroxide, the specific operation steps of which are as follows: Step 1: Add the red mud to a beaker, wash it with 100 ml of deionized water and ethanol respectively, centrifuge, dry at 100℃, and set aside.

[0037] Step 2: Add 4g of red mud and 12g of aluminum chloride at a mass ratio of 3:1. Weigh out 51.91g of sodium dodecyl sulfate (SDS) to be twice the anion exchange capacity of the iron-aluminum LDHs. Mix the red mud, aluminum chloride, and SDS together and place them in a ball mill. Set the speed to 400 rpm and the ball-to-material ratio to 40:1. Perform dry grinding for 5 hours, followed by wet grinding with 2 mL of water for 5 hours. Obtain the organic LDHs. The grinding media used is zirconium balls. The ball-to-material ratio refers to the ratio of the mass of the zirconium balls to the total mass of the red mud, aluminum chloride, and sodium dodecyl sulfate.

[0038] Example 3 This embodiment provides a method for preparing a red mud-based organic layered double hydroxide, the specific operation steps of which are as follows: Step 1: Add the red mud to a beaker, wash it with 100 ml of deionized water and ethanol respectively, centrifuge, dry at 100℃, and set aside.

[0039] Step 2: Add 4g of red mud and 10g of aluminum chloride to the red mud at a mass ratio of 2.5:1. Weigh out 21.63g of sodium dodecyl sulfate (SDS) according to the amount of SDS added being 1 times the anion exchange capacity of the iron-aluminum LDHs. Mix the red mud, aluminum chloride, and SDS together and place them in a ball mill. Set the speed to 370 rpm and the ball-to-material ratio to 20:1. During ball milling, first dry mill for 4.5 hours, then add water for wet milling for 4.5 hours, adding 2.6 mL of water. Organic LDHs are obtained. The grinding media used during grinding is zirconium balls. The ball-to-material ratio refers to the ratio of the mass of the zirconium balls to the total mass of the red mud, aluminum chloride, and sodium dodecyl sulfate.

[0040] Figure 2 In the infrared spectrum of the organic LDHs prepared in Example 1, symmetric and asymmetric stretching vibration absorption peaks of methylene groups were observed, indicating that the organic LDHs were successfully prepared. Figure 2 In this context, intensity is denoted as Intensity.

[0041] Figure 3 and Figure 4 In the XRD pattern, the organic LDHs prepared in Example 1 showed diffraction characteristic peaks in (003), (006), (009), (015), (018), and (113). Among them, the diffraction angle of the (003) diffraction peak was shifted to the left compared with the unmodified diffraction peak, indicating that the interlayer distance of LDHs increased, which was caused by SDS intercalation. Figures 3-4 In this context, 2θ is denoted as 2 theta, and intensity is denoted as Intensity.

[0042] This invention addresses the core shortcomings of existing hydrothermal / coprecipitation methods for preparing organic LDHs. Using red mud as the main raw material, with the addition of aluminum chloride and SDS, a mechanochemical ball milling process is employed. The mechanical force generated by ball milling disrupts the crystal structure of the red mud, releasing divalent and trivalent metal ions, which, along with the Al2+ replenished by aluminum chloride, contribute to the process. 3+ LDHs are formed into a layer, and SDS is driven to insert into the interlayer, ultimately preparing organic LDHs.

[0043] This invention utilizes the synergistic effect of mechanochemical ball milling and red mud resource utilization to successfully prepare organic LDHs. The following description covers four main aspects: technical solution, economy, environmental protection, and application.

[0044] (I) Technical Solution: 1. Breaking through the dependence on pure chemical raw materials, achieving low-cost resource utilization of raw materials while ensuring product performance meets standards. By optimizing ball milling process parameters (ball-to-material ratio, rotation speed, and time), efficient release of metal ions from red mud and in-situ generation of LDHs layers are achieved. Without the need for pH adjustment with alkali solution and complex crystallization, products with stable interlayer structure and good intercalation effect can be prepared using only red mud as the main raw material. The performance is no less than that of existing technologies, and the adsorption performance is even more advantageous due to the porous nature of red mud.

[0045] 2. Completely solves waste liquid pollution and achieves green and clean production. This invention constructs a solid-phase mechanical chemical reaction system. The ball milling process does not require the addition of water or excess alkali solution. No washing is required after the reaction, and no waste liquid is generated. Only a small amount of dust can be easily treated, eliminating pollution at the source and avoiding the process and cost burden of existing waste liquid treatment technologies.

[0046] 3. Improve raw material utilization, reduce energy consumption, and enhance technical feasibility and safety. Ball milling enables the release rate of metal ions from red mud to reach over 85%. Specifically, the release rate of metal ions from the red mud in Example 1 was tested by ICP, and the release rate was 87.5%, which is much higher than existing technologies (60%~80%). For example, the release rate recorded by Liu Y et al. in "Hidden values ​​in bauxite residue (red mud): Recovery of valuable metals" published in "Waste Management" in 2014 was 75.7%~80.7%. The reaction is carried out at room temperature and pressure without high temperature and high pressure, and the energy consumption is only 15%~20% of that of the hydrothermal method and 30%~40% of that of the coprecipitation method. There are no safety hazards, making it more suitable for large-scale production.

[0047] 4. Simplify the process flow and achieve continuous production. Eliminate the steps of dissolving, adjusting pH, crystallizing, and washing in existing technologies. After mixing the raw materials, the product can be obtained directly by ball milling and sieving. The production cycle is shortened from 10-24 hours to 2-6 hours, improving efficiency and reducing labor and equipment costs.

[0048] (II) Economic Benefits: The present invention offers significant economic benefits, primarily stemming from the cost savings and increased profits resulting from the implementation of the technical solution. The calculations are based on an annual production capacity of 1000 tons, as follows: 1. Significantly reduced raw material costs, enhancing market competitiveness. Existing technologies have raw material costs of 8,000-10,000 yuan / ton. This invention uses low-cost red mud (requiring only 50-100 yuan / ton in transportation costs) as the main raw material, supplemented with a small amount of aluminum chloride and SDS, reducing the total cost to 1,500-2,000 yuan / ton, a reduction of over 75%.

[0049] 2. Reduces waste liquid treatment costs and lowers environmental protection investment. Existing technologies cost 800-1200 yuan / ton of product to treat waste liquid. This invention produces no waste liquid, saving 800,000-1,200,000 yuan annually.

[0050] 3. Optimize energy consumption and efficiency to increase profit margins. Annual energy cost savings of 500,000 to 800,000 yuan, production efficiency increased by 3 to 5 times, and additional revenue of 400,000 to 600,000 yuan.

[0051] 4. Expand red mud disposal channels to generate additional revenue. Consuming 800-900 tons of red mud annually can save on disposal costs and generate additional revenue of 40,000 to 72,000 yuan by collecting processing fees.

[0052] In summary, this can save costs and increase revenue by a total of RMB 2 million to RMB 2.7 million annually.

[0053] (III) Environmental benefits: 1. Achieve the reduction and resource utilization of red mud, and reduce solid waste accumulation pollution.

[0054] 2. No waste liquid discharge, avoiding water and soil pollution, meeting environmental protection requirements.

[0055] 3. Reduce energy consumption and carbon emissions.

[0056] (iv) Application benefits: The product has a low cost. Based on the raw material price, red mud costs more than 1,000 yuan per ton, while traditional iron oxide costs about 100,000 yuan per ton. The preparation cost of this invention is even lower. The organic LDHs have complete structural characteristics and can be widely used in adsorption, catalysis, flame retardancy, pesticide slow release and other fields. It can replace existing high-priced products and promote the upgrading of related industries.

[0057] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0058] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a red mud-based organic layered double hydroxide, characterized in that, Prepare according to the following steps: Red mud was used as a source of divalent metal ions and trivalent aluminum ions, and an organic intercalating agent was used as a source of organic anions. The red mud, aluminum salt and organic intercalating agent were ball-milled, and the red mud and aluminum salt underwent solid-phase co-precipitation to form a positively charged iron-aluminum layered bimetallic hydroxide. The organic anions were intercalated into the interlayer of the iron-aluminum layered bimetallic hydroxide to obtain a red mud-based organic layered bimetallic hydroxide. The mass ratio of red mud to aluminum salt was 1:2 to 3.

2. The method for preparing a red mud-based organic layered double hydroxide according to claim 1, characterized in that, Based on the anion exchange capacity of the iron-aluminum layered bimetallic hydroxide formed by red mud and aluminum salt, the added mass of the organic intercalating agent is 1.0 to 2.0 times the anion exchange capacity of the iron-aluminum layered bimetallic hydroxide.

3. The method for preparing a red mud-based organic layered double hydroxide according to claim 1, characterized in that, During ball milling, the rotation speed is 350 rpm to 400 rpm.

4. The method for preparing a red mud-based organic layered double hydroxide according to claim 1, characterized in that, When ball milling, first dry mill for 4 to 5 hours, then add water and wet mill for 4 to 5 hours.

5. The method for preparing a red mud-based organic layered double hydroxide according to claim 5, characterized in that, The ratio of red mud to water is 1g to 2g: 1ml.

6. The method for preparing a red mud-based organic layered double hydroxide according to claim 1, characterized in that, During ball milling, the ball-to-material ratio is 40–20:

1.

7. The method for preparing a red mud-based organic layered double hydroxide according to claim 1, characterized in that, The organic intercalating agent is sodium dodecyl sulfate, and the aluminum salt is aluminum chloride.

8. A red mud-based organic layered double hydroxide prepared by the preparation method according to any one of claims 1 to 7.

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